1. Field of the Invention
The present invention relates to a method and apparatus for measuring, by using an image processing technology, a pattern of an article to be tested, such as a dial plate (figured plate) for a measuring instrument or a mask with a pattern for a wafer for producing a semiconductor.
2. Description of Related Art
A known prior art device measures a deviation of a pattern, wherein an image to be detected is, under a pixel to pixel basis, compared with a reference image, thereby detecting a deviation of the detected image from the reference image. In order to increase a calculation speed, the Japanese Unexamined Patent Publication 3-167407 has proposed the use of a part or section of the reference image, which is then compared with the detected image. However, such a use of partial image is defective due to its low precision of measurement.